The price reflects the pressure on heavily overfished Pacific bluefin stocks and the popularity of sushi in Japan and around the world.

A single Pacific bluefin tuna sold for 36.45 million yen (US$323,111) during the famed New Year auction at Tokyo’s Tsukiji fish market on Jan. 5.

The sale took place amid ongoing concerns over the status of stocks of the species, Thunnus orientalis.

Tsukiji is reputedly the world’s oldest and largest fish market. Since opening in 1935, it has become a popular tourist attraction that is most famous for its daily predawn auctions of tuna, bought by local grocery store staff and chefs at top restaurants alike. But the first tuna auction of the year has special significance, as traders vie to show off their business’s prosperity and gain public exposure. Some regard it as a portent of the coming year’s business.

“The Tsukiji tuna auction at the beginning of the year is an important ceremony for the parties concerned with [the] market,” Yoshifumi Sawada, an expert in Pacific bluefin aquaculture at the Oshima Experiment Station of Osaka’s Kindai University, told Mongabay. He added that in Japan, spending exorbitantly on products such as raw tuna is considered “refined.” The recent New Year auction was Tsukiji’s last before the market moves to a new location later this year.

The US$323,111 price, paid for a 405-kilogram (892-pound) tuna, reflects the pressure on heavily overfished Pacific bluefin stocks and the popularity of sushi in Japan and around the world. It was, however, around half the price of last year’s highest bid of about 72 million yen and much lower than the record 155 million yen (US$1.8 million) paid in 2013.

“The high price paid today for a single Pacific bluefin tuna should not distract from the dire status of the species, which has been depleted by more than 97 percent by years of overfishing,” Jamie Gibbon, global tuna conservation officer for the Washington, D.C.-based Pew Charitable Trusts, said in a statement shared with Mongabay on the day of the Tsukiji auction.

Pacific bluefin stocks have been declining for many years as a result of overfishing. Of particular concern is that catches consist predominantly of juveniles not yet able to reproduce and help replenish the species. Many of them are raised to marketable size in pens.

In 2014, the International Union for the Conservation of Nature listed Pacific bluefin as “vulnerable,” a designation for species facing a “high risk of extinction in the wild.” In April 2016, an assessment of Pacific bluefin tuna stocks published by the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean stated that spawning bluefin stocks had declined to just 2.6 percent of theoretical pre-fishing levels.

Adult bluefins, a top predator, can weigh over 450 kilograms (1,000 pounds) and migrate thousands of miles. Known as kuro-maguro or hon-maguro in Japanese, they are prized for sushi and sashimi.

In September, an international agreement to rebuild Pacific bluefin stocks emerged from a meeting held in South Korea between the two organizations charged with managing the species: the Western and Central Pacific Fisheries Commission and the Inter-American Tropical Tuna Commission. There, the main bluefin-fishing nations of Japan, South Korea, Taiwan, Mexico and the United States agreed with other member states to rebuild bluefin populations to 20 percent of pre-fishing levels by 2034. This would bring the population to a sustainable level and pave the way for a new, long-term management plan. The members also agreed to reduce catch levels immediately if there was a less than 60 percent chance of meeting the 2034 target, and to consider raising catch quotas during the next seven years only if there is a 75 percent chance of meeting the target.

As the world’s biggest consumer of bluefin, Japan’s commitment to rebuilding was a long time coming, and the agreement caps several prior failed attempts. Conservationists have welcomed the agreement, albeit with caution.

“There was hope late last year when governments agreed on a rebuilding plan that could secure the long-term future of the species,” Gibbon said in the statement. “However, if this highly prized species is to truly recover, it is critical that the rebuilding plan is successfully implemented by all of the nations who fish for Pacific bluefin. If countries continue to exceed their catch limits, as they have in recent years, the very survival of the species will be threatened.”

Similarly, when the agreement was announced, Monterey Bay Aquarium in California issued a statement saying that countries will need to be vigilant and commit to fulfilling their responsibilities under the agreement, including monitoring catches, enforcing quotas and investing in more research on the biology and migration routes of bluefin.

To that end, aquaculture may offer a solution. Sawada and other researchers at Kindai University pioneered rearing Pacific bluefin in captivity through their full life cycle in 2002. It takes at least five years to raise the tuna from egg to reproductive adulthood, when they reach a size of 2 meters they weigh 200 kilograms. Aquaculturists gather fertilized eggs from the water surface, which hatch into larvae after around 32 hours. It then takes 40 days for the larvae to grow into fry, at which point they are moved from tanks on land to net enclosures in the open ocean. After around three years, they are shipped to market when they reach more than a meter long and weigh around 30 kilograms (66 pounds).

But bluefin are difficult to rear in captivity. With highly sensitive reactions to light and sound, they are known to swim at top speed and die on impact with the sides of tanks or nets. Most frustratingly, they rarely spawn in captivity and even when they do, only a tiny number of offspring survive. Eggs and larvae are so fragile that simply touching the side of a tank can kill them.

How to feed tuna sustainably poses another hurdle. Tuna consume vast amounts of fish meal so the Kindai University team is currently looking at alternatives, such as plant protein, that won’t entail harvesting wild fish.

Despite the challenges, as well as skepticism from some scientists and conservationists that aquaculture can produce predatory fish sustainably, Sawada believes in completely farm-raised bluefin and is hopeful that one day his research will contribute significantly to the protection of wild bluefin stocks.

Sawada said the agreement is an important first step in tuna management. “However, such effort must be continued with great patience until the resource managing system is completed scientifically and politically,” he said. Arguing that aquaculture research can provide insights into Pacific bluefin ecology and genetics, he added, “If such information obtained in the aquaculture research is combined with the field research information, it will contribute greatly [to] the management of tuna resources.”

As this year’s trading gets underway at Tsukiji market, experts will be watching closely to see whether the world’s tuna-fishing nations will make good on their agreement to preserve one of the ocean’s most iconic species.

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The News Lens has been authorized to publish this article from Mongabay, an environmental science and conservation news and information site.

TNL Editor: Morley J Weston